<template>
  <div class="spec-preview">
    <img :src="smallImg" />
    <div class="event" @mousemove="move" ref="event"></div>
    <div class="big">
      <img :src="bigImg" ref="bigImg" />
    </div>
    <div class="mask" ref="mask"></div>
  </div>
</template>

<script>
export default {
  name: "Zoom",
  props: {
    smallImg: String,
    bigImg: String,
  },
  //
  // mounted() {
  //   //maskWidth -> 不需要定义到data里--》非响应式的数据【数据不变】
  //   this.maskWidth = this.$refs.event.clientWidth / 2;
  // },
  methods: {
    //中图的鼠标移动事件
    move(event) {
      let left, top;
      const maskDiv = this.$refs.mask;
      const bigImg = this.$refs.bigImg;
      const { offsetX, offsetY } = event;
      const maskWidth = maskDiv.clientWidth;

      //left 和 top 计算
      left = offsetX - maskWidth / 2;
      top = offsetY - maskWidth / 2;

      left = left < 0 ? "0" : left > maskWidth ? maskWidth : left;
      top = top < 0 ? "0" : top > maskWidth ? maskWidth : top;

      //mask 的top 和 left 值
      maskDiv.style.left = left + "px";
      maskDiv.style.top = top + "px";

      //bigImg 的 top 和 left 值
      bigImg.style.left = -2 * left + "px";
      bigImg.style.top = -2 * top + "px";
    },
  },
};
</script>

<style lang="less">
.spec-preview {
  position: relative;
  width: 400px;
  height: 400px;
  border: 1px solid #ccc;

  img {
    width: 100%;
    height: 100%;
  }

  .event {
    width: 100%;
    height: 100%;
    position: absolute;
    top: 0;
    left: 0;
    z-index: 998;
  }

  .mask {
    width: 50%;
    height: 50%;
    background-color: rgba(0, 255, 0, 0.3);
    position: absolute;
    left: 0;
    top: 0;
    display: none;
  }

  .big {
    width: 100%;
    height: 100%;
    position: absolute;
    top: -1px;
    left: 100%;
    border: 1px solid #aaa;
    overflow: hidden;
    z-index: 998;
    display: none;
    background: white;

    img {
      width: 200%;
      max-width: 200%;
      height: 200%;
      position: absolute;
      left: 0;
      top: 0;
    }
  }

  .event:hover ~ .mask,
  .event:hover ~ .big {
    display: block;
  }
}
</style>